if eggs are fertilized at the wrong time of the month then the zygote still gets aborted just as part of the normal menstrual cycle.
Yes, but that is God's work, not human's. You didn't take an overt action to cause it.
In other words, people die all the time, sometimes for good reasons, sometimes for no reason at all. That doesn't make them bad, it is just life. You go when it is your time to go.
There is a difference between billions of fertile eggs dying every year due to nature and millions killed on purpose.
That is why the law, for example, splits out homicide between intentional and unintentional, and sometimes you can kill someone and not go to jail because it was an honest accident due to events beyond your control.
Note: I fully get that not everyone agrees with me, thus the willingness to compromise. I give my point of view and set my position, then figure out what I can actually get, because I don't live in a world that has to do what I say. I honestly wish BOTH sides would remember that, because I hear it too often from both extremes that they don't wish to be reasonable.
Good job on the birth control thing - if you legitimately believe that way and are willing to forgo all contraceptive pills in your family based on your beliefs, that puts you a good step above most pro-lifers.
That said, I don't think the distinction on how a fetus gets aborted matters. The "rhythm method" of contraception has been around for a long, long time, and it plain and simple doesn't prevent eggs from being fertilized. Are these people committing continual manslaughter? Honestly, if you really go that far, then I think it might become immoral to have kids at all, or ever risk activity that would allow a fertilized egg to be aborted by natural causes or otherwise.
Think about it like this: if you want to save a kid's life, is it worth risking another kid's life for every chance at it? Obviously the answer is no. Every time you attempt to conceive, you run a serious risk of aborting a fertilized egg. By your definition, there's no moral way to conceive a child unless you can do it in such a way that you guarantee that no zygote can be aborted - and there is no way to get that guarantee.
The whole "natural" vs. "unnatural" thing is nonsense. Rape is natural, considering that it happens in the animal kingdom everywhere. Malaria is natural, so clearly there's no moral problem with allowing a child to die from malaria, right? Whether you make a choice that has a large chance of killing a child, or you outright choose to kill a child, you have done something horrific. I have found no logical argument that allowing a zygote to abort from natural causes is manslaughter, ergo early term abortion is not murder.